Detection: Windows Powershell Connect to Internet With Hidden Window

Description

The following hunting analytic identifies PowerShell commands utilizing the WindowStyle parameter to hide the window on the compromised endpoint. This combination of command-line options is suspicious because it is overriding the default PowerShell execution policy, attempts to hide its activity from the user, and connects to the Internet. Removed in this version of the query is New-Object. The analytic identifies all variations of WindowStyle, as PowerShell allows the ability to shorten the parameter. For example w, win, windowsty and so forth. In addition, through our research it was identified that PowerShell will interpret different command switch types beyond the hyphen. We have added endash, emdash, horizontal bar, and forward slash.

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Implementation

You must be ingesting data that records process activity from your hosts to populate the Endpoint data model in the Processes node. You must also be ingesting logs with both the process name and command line from your endpoints. The command-line arguments are mapped to the "process" field in the Endpoint data model.

Known False Positives

Legitimate process can have this combination of command-line options, but it's not common.

Associated Analytic Story

• Malicious PowerShell

• Possible Backdoor Activity Associated With MUDCARP Espionage Campaigns

• HAFNIUM Group

• Log4Shell CVE-2021-44228

Risk Based Analytics (RBA)

References

• https://regexr.com/663rr

• https://github.com/redcanaryco/AtomicTestHarnesses/blob/master/Windows/TestHarnesses/T1059.001_PowerShell/OutPowerShellCommandLineParameter.ps1

• https://ss64.com/ps/powershell.html

• https://twitter.com/M_haggis/status/1440758396534214658?s=20

• https://blog.netlab.360.com/ten-families-of-malicious-samples-are-spreading-using-the-log4j2-vulnerability-now/

Version: 6